This invention relates to a method of inhibiting deposition or precipitation of iron salts in aqueous systems which comprises adding a urea salt to said systems.
The literature discloses numerous references for scale and corrosion inhibition and iron stabilization in aqueous systems by employing polymers or copolymers of sulfonic acid/acrylic acid (SA/AA) or acrylic acid/hydroxy propyl acrylate (AA/HPA) as well as polyphosphates and phosphonates. For example, see below:
(1) U.S. Pat. No. 4,640,793 discloses an admixture, and its use in inhibiting scale and corrosion in aqueous systems comprising:
(a) a water-soluble polymer having a weight average molecular weight of less than 25,000, as determined by low angle laser light scattering, comprising an unsaturated carboxylic acid and an unsaturated sulfonic acid, or their salts, having a ratio of 1:20 to 20:1, and PA1 (b) at least one compound selected from the group consisting of water-soluble polycarboxylates, phosphonates, phosphates, polyphosphates, metal salts and sulfonates.
Said patent is also directed to a method of inhibiting the formation of insoluble alluvial, metal oxide, and metal hydroxide deposits in an aqueous system, comprising adding to the system at least 0.1 mg/l of a water-soluble polymer having a weight average molecular weight of less than 25,000, as determined by low angle laser light scattering, comprising an unsaturated carboxylic acid and an unsaturated sulfonic acid, or their salt, having a ratio of 1:20 to 20:1 and a phosphate.
(2) U.S. Pat. No. 3,959,167 (1976)--discloses a method for using a new improved composition for inhibiting or preventing accumulation of scale or the like on heating surfaces in an aqueous system. The composition includes an acrylic polymer, a water-soluble chelant, and an organophosphonic acid and/or their water-soluble salts. In a preferred embodiment, the composition is composed of sodium polymethylacrylate, nitrilotriacetic acid and hydroxyethylidene diphosphonic acid as its water-soluble salts.
(3) U.S. Pat. No. 4,552,665 (1985)--discloses a process for inhibiting the precipitation of dissolved manganese ion and its reaction products in aqueous solutions, comprising adding to said aqueous solution 0.1 to 20 ppm of a copolymer of an unsaturated carboxylic acid or salt selected from the group consisting of acrylic acid and methacrylic acid and an unsaturated sulphonic acid or salt selected from the group consisting of 2-acrylamido-2-methylpropylsulphonic acid and 2-methacrylamido-2-methylpropylsulphonic acid.
(4) U.S. Pat. No. 4,537,684 discloses a method for controlling the deposition of metal-containing scales, such as iron silicate scale, from a hot, aqueous, geothermal brine or the like, without substantial corrosion of brine handling equipment. The brine is contacted with (1) an amount of an acid sufficient to reduce the pH of the brine between 0.1 and 0.5 unit and (2) a greater than stoichiometric amount of a reducing agent for reducing trivalent iron and manganese cations in a high temperature brine solution to divalent ions. An overall decrease in scale deposition, especially of iron silicate scale, is achieved while a silver-rich scale can be recovered from silver-containing brines.